In order to achieve efficient heat transfer with minimum temperature drop between the heatsink and coldwall, adjacent parts, intimate, large area mechanical contact is necessary. In an attempt to also accommodate for dimensional changes over a temperature range, some previous devices incorporated therein fairly thin resilient sheet stock formed to act as a spring as well as a thermally conductive member. Such devices have narrow cross sections and have small contact areas with low interface clamping force that limits heat transfer. In order to achieve maximized heat transfer, there is need for a high pressure, optimum clamp structure.